Pilot misjudgment and an over-reliance on automated systems were the main causes of last year's crash of Asiana Flight 214 in San Francisco that killed three people, the National Transportation Safety Board concluded Tuesday.

The Boeing 777 with 307 people aboard came in too low and too slow in its landing approach, the NTSB said. It hit a seawall, ripping off the tail and sending the plane's fuselage skidding down the tarmac.

The board said there was confusion over whether the plane was maintaining adequate speed for landing.

Acting NTSB Chairman Chris Hart said at a meeting ahead of the agency's vote on its conclusions that the crew "over-relied on automated systems that they did not fully understand."

He also cited the complexity of the 777's autothrottle and pilot training by the South Korea-based airline, according to The Associated Press.

"In their efforts to compensate for the unreliability of human performance, the designers of automated control systems have unwittingly created opportunities for new error types that can be even more serious than those they were seeking to avoid," Hart said.

The BBC writes:

"Asiana has acknowledged the crew failed to monitor and maintain the plane's airspeed, which was likely to have been the cause of the accident, according to documents made public by the NTSB.

"The South Korea-based airline said those flying the plane reasonably believed the automatic throttle would keep the plane flying fast enough to land safely.

"But that feature was shut off after a pilot idled it to correct an unexplained climb earlier in the landing.

"The airline argued the automated system should have been designed so that the auto throttle would maintain the proper speed after the pilot put it in 'hold mode.' "

Update at 3:20 p.m. ET. Asiana Says NTSB 'Properly Recognized' Problems:

In a statement released after the NTSB's determination on Tuesday, Asiana Airlines said:

"We believe the National Transportation Safety Board (NTSB) has properly recognized the multiple factors that contributed to the accident, including the complexities of the autothrottle and autopilot systems, which the agency found were inadequately described by Boeing in its training and operational manuals. The recommendations made by the agency can help ensure such an incident does not happen again.

"We again express our great sorrow for the accident, the loss of life and the injuries sustained by the passengers and crew.

"The NTSB made four training recommendations to Asiana, all of which Asiana has already implemented. In addition, since last July's accident, Asiana has on its own enhanced flight crew training and evaluation, strengthened flight instructor training, enhanced crew resource management training, and revamped our safety management structure. As a part of this initiative, we also hired Akiyoshi Yamamura, an outside safety specialist with broad international experience as the airline's new Executive Senior Vice President of Safety."

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